A search directed to the present invention located the following United States patents directed to racks and holders for scuba tanks and other types of gas tanks and cylinders: 4,168,007, issued Sep. 18, 1979, 5,025,935, issued Jun. 25, 1971, 4,391,377, issued Jul. 5, 1983, 4,899,895, issued Feb. 13, 1990, and 3,602,368, issued Aug. 31, 1971.
U.S. Pat. No. 5,025,935, issued Jun. 25, 1991, is of particular note in that the patent discloses a scuba cylinder retention rack for attachment to the bed of a pickup truck. The patent also suggests the possibility of attaching the portable retention rack to a boat. The rack of U.S. Pat. No. 5,025,935 is not positively held in place, but rather maintained in position by a spring biased element. Furthermore, the rack is only connected or associated with one side of the vehicle, and sliding between the rack and vehicle can occur. The cylinder or cylinders held by the rack are not elevated relative to the floor of the pickup bed and, in fact, the tank bottoms are positioned directly on the floor of the pickup bed. This means that any cylinder in the rack can fall through the bottom thereof and not be transported thereby when the rack is removed from its location of attachment to the pickup bed.
U.S. Pat. No. 4,345,861, issued Aug. 24, 1982, discloses a support system for large, generally cylindrical tanks in ships. The teachings of this patent do not appear to be at all applicable to racking and storage of scuba tanks. The tanks disclosed in the patent are essentially for permanent installation in a vessel and relate particularly to the transportation of large quantities of LNG.
U.S. Pat. No. 4,842,175, issued Jun. 27, 1989, relates to a general type of storage container for storing articles in the interior of an automobile. The arrangement does not appear to be applicable to the storage of scuba tanks. The storage container utilizes end stabilizers, such as screw clamps, to stabilize the storage elements of the apparatus with respect to the vertical walls of the interior of the automobile. A somewhat similar arrangement is shown in U.S. Pat. No. 4,944,544, issued Jul. 31, 1990. The stabilizing approaches of these latter two patents would not lend themselves to attachment to a relatively resilient surface such as the side of an inflated boat.